Words of Power shapechanging spells.

The lowest level change word of power is level 3 compared to alter self's level 2; which is also circumstantially more powerful. Is this because alter self is too poweful for its level but was left there due to tradition?

Also I was planning on introducing a words of power system to my game and was thinking of removing the +2 to strength bonus and instead making one of the options to select an ability boost lesser in degree than the bull's strength things but maybe affecting 3 stats? Are there any glaring issues with this? What would be the implications?